The capabilities of cellular handheld devices increase every day as advances in microchip technology and able more circuits and functionality to be built into the devices. Consequently, cellular handheld devices have quickly evolved beyond simple communication devices to becoming personal communication/entertainment/information resources.
One source of information that has not been incorporated into cellular handheld devices is the Radio Data Systems (RDS) which communicates data to properly equipped FM radios as part of a normal FM radio broadcast. While some cellular devices have incorporated an FM receiver to enable users to listen to radio, none have made use of the RDS signals to provide interactive services. RDS is a technology that has been deployed in several countries around the world. Within the United States, the equivalent system is known as the radio broadcast data system (RBDS). For simplicity, references to RDS herein are intended to encompass RBDS, and the description of RDS technology is based on the U.S. RBDS implementation.
The RDS system makes use of a 57 kilohertz wide sub carrier within an FM frequency band to transmit a low data rate signal. The RDS data stream is produced by the FM broadcaster, and so is unique to the broadcasting station. Not all FM broadcasts include RDS data, as it is an option available to broadcasters, but not a requirement. Data is transmitted at a rate of 1187.5 bits per second, but with error encoding and other overhead communication, the system transmits about 300 bits per second of usable data. This data may be obtained by any FM radio including the necessary circuitry in functionality to receive and code the RDS Signal.
RDS data is transmitted into continuous stream of 16-bit packets illustrated in FIG. 1 which are transmitted in an endless repetition. The 16-bit packets are also referred to as data blocks. These packets come in four varieties based upon the pattern of bits in packet, referred to as types A, B, C, and D, each of which carries a different type of data as defined in the RDS standards. For example, the type A blocks contain the radio station call sign, type B blocks contain control information, type C blocks contain either the station call sign or data, and type D blocks contain data. The four types of blocks can be arranged into specific arrangements called groups of which there are 32 types, 16 type A groups and 16 type B groups. RDS standards define the content for each of these blocks and groups or types of data packets.
Referring to FIG. the 1, the first four bits (bits 12-15 in FIG. 1) within an RDS block are used to define the particular group number of the data packet. The fifth bit (bit 11) indicates whether the group is of type A (bit 5=0) or type B (bit 5=1). The sixth bit (bit 10) may be used for highway traffic announcement related indicators, and is referred to as the TP bit. The TP bit along with a subsequent bit known as the TA bit (bit 4) are used to transmit information regarding the availability of a traffic announcement, as illustrated in FIG. 2. Following the TP bit are five PTY bits (bits 5-9) that are used in some data packets to indicate the type of program carried on the FM station, according to the code table shown in FIG. 3. As shown in FIG. 3, the five PTY bits are used to provide a binary value (or bit pattern) that corresponds a particular type of programming that is being broadcast by the FM radio station. The remaining bits may be used to carry additional codes depending upon the type of group.
The use of the RDS data communication capability is expanding as new applications are identified and better coding systems are developed. With increased data encoding capability, additional types of information can be made available for use in a variety applications. An example of expansion of the RDS system capability is illustrated in U.S. Pat. No. 6,411,800 the entire contents of which are hereby incorporated by reference.